Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2015

Compensation and Retirement Disclosure [Abstract]

Components of Net Periodic Benefit Cost

The components of the net periodic pension benefit costs for the three months ended March 31 were as follows:

	2015			2014
	(Dollars in thousands)
Service cost	$	4,050		$	3,455
Interest cost	7,149			7,430
Expected return on plan assets	(15,655		)	(14,355		)
Amortization of prior service cost	246			285
Amortization of actuarial losses	1,833			217
Net periodic benefit credit	$	(2,377	)	$	(2,968	)

The components of the net periodic other postretirement benefits costs for the three months ended March 31 were as follows:

	2015			2014
	(Dollars in thousands)
Service cost	$	143		$	138
Interest cost	360			408
Amortization of prior service credit	(736		)	(714		)
Amortization of actuarial gains	(64		)	(85		)
Net periodic benefit credit	$	(297	)	$	(253	)